This invention relates to a process for the preparation of chroman-4-ones, and to chroman-4-ones produced thereby.
It is known to prepare 2-aryl-chroman-4-ones by reacting benzaldehydes with o-hydroxyacetophenones. A disadvantage of this process is that mixtures of different compounds are formed and that the reaction takes up to 83 days (Elderfield, Heterocyclic Compounds, volume 2, page 347).
Furthermore, chroman-4-ones can be prepared by the reaction of phenols with .alpha.,.beta.-unsaturated carboxylic acid chlorides and subsequent rearrangement of the reaction product (Bull. Soc. Chem. Belge 82, 705 (1973)). A disadvantage of this process is the use of a large excess of polyphosphoric acid, which cannot be re-used.
It is also possible to prepare chroman-4-ones by cyclisation of .beta.-aryloxypropionic acids in the presence of a Friedel-Crafts catalyst (European Journal of Medicinal Chemistry, 1975, 257). Large amounts of the Friedel-Crafts catalyst, the removal of which is involved and gives rise to pollution of the environment, are necessary in order to carry out this process.